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Two-thirds of people don’t sleep enough. Do you? 💤

Two-thirds of adults throughout all developed nations fail to obtain the recommended eight hours of nightly sleep. Okay I know, this fact alone might not surprise you, since you are probably one of them. But the consequences of this lack of sleep might; routinely sleeping less than six or seven hours a night demolishes your immune system, doubles your risk of cancer, is a key lifestyle factor determining whether or not you will develop Alzheimer’s disease, disrupts blood sugar levels and contributes to all major psychiatric conditions, including depression, anxiety and suicidality.

Matthew Walker knows the great benefits sleep offers. He is a professor of neuroscience and psychology at UC Berkeley. Before that he was professor of psychiatry at Harvard Medical School. He’s been a researcher for over 20 years, focusing mostly on sleep. With his book “Why We Sleep”, which we are talking about in today’s Blog post, he has made abundantly clear that sleep is one of the most important but least understood aspects of our life.


Until very recently, science had no answer to the question of why we sleep, or what good it served, or why we suffer such devastating health consequences when it is absent. Society’s apathy toward sleep has, in part, been caused by this historic failure of science to explain why we need it. Sleep remained one of the last great biological mysteries.

So it is not really surprising that modern people don’t seem to value sleep. Despite the fact that we spend one-third of our lives sleeping. In schools we are usually taught the importance of healthy eating and exercise. However, we are not taught why it’s important to sleep or how to sleep better. Even worse, many people almost consider it a badge of honor to function on little sleep in the name of higher productivity or success.

“The WHO has now declared a sleep loss epidemic throughout industrialized nations.” - National Geographic

It is no coincidence that countries where sleep time has declined most dramatically over the past century, like several in western Europe, are also those suffering the greatest increase in rates of physical diseases and mental disorders.

In case you, like many others, never thought about why sleep is important, this book makes the data clear – sleep is vital to our health and has the ability to make us smarter, more attractive, slimmer, and happier. Matthew Walker is on a mission to change our attitude about sleep with a book that aims to demystify what sleep is, warn us of the consequences of sleep deprivation, explain the fantastical world of dreams, and give us reliable and practical advice for helping society get more zzz’s.

So it’s definitely time to talk about this mystery and make sleep cool again!


But before we dive into it, let’s answer the most important question; are YOU getting enough sleep?

Two rules of thumb:

  1. After waking up in the morning, could you fall back asleep at ten or eleven a.m.? If yes, then you’re probably not getting enough quality sleep.

  2. Can you function optimally without caffeine before noon? If no, then you are most likely self-medicating your state of chronic sleep deprivation.

Okay, now that we clarified this, let's first cover some theoretical background on sleep.

Two Types of Sleep

  1. NREM = Non-rapid eye movement with four stages of increasing depth

  2. REM = Rapid eye movemen: Brain activity almost identical to when we’re awake & associated with dreaming

NREM and REM stages play out in a recurring, push-pull battle for brain domination across the night in 90-minute intervals.

  • A key function of deep NREM sleep, which predominates early in the night, is to do the work of weeding out and removing unnecessary neural connections.

  • The dreaming stage of REM sleep, which prevails later in the night, plays a role in strengthening those connections.

📍 The last 2 hours of nightly sleep are most important for consolidating memory. Why? Because that’s when we get the most stage 2 REM sleep and sleep spindles. This is important because if you cut your sleep short in the morning, then you will lose a disproportionate amount of the sleep that is beneficial to memory.

Two factors that determine when we want to sleep and when we want to be awake:

  1. The suprachiasmatic nucleus: an internal 24-hour clock located deep within your brain.

    1. Jet lag is caused by speeding through time zones without letting your biological clock catch up. For every day you are in a different time zone, your suprachiasmatic nucleus can only readjust by about one hour.

  2. Adenosine: a chemical substance that builds up in your brain and creates a “sleep pressure” inside of us the longer we stay awake. After 12-16 hours of being awake most people will get a very strong urge to go to sleep, which is caused by rising levels of adenosine in your brain.

    1. Caffeine works by successfully battling with adenosine for the privilege of latching on to adenosine welcome sites — or receptors — in the brain. By hijacking and occupying these receptors, caffeine blocks the sleepiness signal normally communicated to the brain by adenosine. When you drink caffeine, 5-7 hours later half the caffeine is still in your system. So you should generally avoid drinking it late in the afternoon. Most people underestimate how long it takes our bodies to flush out caffeine. This can lead to major sleep problems.

Don't believe me? Check out the following research done by NASA, exposing spiders to different drugs. It is worth pointing out that caffeine is a stimulant drug & the only addictive drug readily accepted in our society, making it the most widely used (and abused) stimulant in the world.

[P. 30 FIGURE 3]

My Rhythm Is Not Your Rhythm

  • 40% of the population reaches peak wakefulness in the morning.

  • 30% are more energized in the evening.

  • 30% fall somewhere in between, with a slight leaning toward the evening.

  • An adult’s owlness or larkness, also known as their chronotype, is strongly determined by genetics.

  • Our society’s work schedule puts night owls at a disadvantage and favors those who are more energized in the morning. Like having to wake up at 7 or 8am to commute to a 9-5 job. Because of that, night owls are often labeled as “lazy”, since they don't like to wake up until later in the morning. Even though they are actually just following a built in natural rhythm. As a consequence, evening types are often forced into an unnatural sleep-wake rhythm to meet a certain work schedule, thus evening types are more often sleep-deprived.

  • Teenagers universally stay up later and have trouble getting up. This is because during adolescence the inner clock shifts later. Teens don’t stay up to be rebellious (at least not always) but because their circadian rhythm makes them not feel sleepy at 10pm. It’s like asking an adult to go sleep at 7pm. This of course presents a conflict with early school start times.


Okay, this is enough of the theory behind it, let's get to the really interesting facts that had a powerful effect on me... and hopefully you too - never thinking of your bedtime in the same way again!

📍 Sleep is universal. Without exception, every animal species studied to date sleeps, or engages in something remarkably like it. From the point of view of survival and evolution, sleep only makes sense if it is absolutely essential to life. There is little that makes an animal more helpless than needing to slip into a coma for hours every night. Yet all animals sleep, from insects to fish to frogs and birds and mice and tigers, bears, chimps and humans.

  • The total amount of time is one of the most conspicuous differences in how organisms sleep; elephants sleep just 4 hours. Brown bats sleep 19 hours.

  • Not all species experience all stages of sleep: insects, amphibians, fish, and most reptiles show no clear signs of REM sleep — the type associated with dreaming in humans.

  • Cetaceans (such as dolphins and whales) and birds sleep with half a brain at a time. That's how some birds are actually sleeping while in flight.

  • Human beings are the only species that will deliberately deprive themselves of sleep without legitimate gain.

📍 People often try to “catch up” on sleep during the weekend. Especially when they have a habit of sleeping too little during the week. But missing sleep is not like a credit card debt that you can simply pay back later. There are real consequences to sleep deprivation, especially when it comes to learning and memory. The brain can never recover all the sleep it has been deprived of.

📍 Most cultures that have not been touched by technology sleep in a biphasic pattern. This means they sleep at night for 7-8 hours, and also have a 30-60 minute nap each afternoon. This pattern has been observed in hunter-gatherer tribes in Africa. Biphasic sleep is also popular in many Mediterranean countries like Spain, Italy and Greece. These countries have a “siesta” culture of taking an afternoon nap during the hottest part of the day. A study of 30'000 Greeks found that people who took these afternoon naps were significantly less likely to die of a heart attack. Unfortunately, this practice is now far less popular among younger working people than the older generation.

📍 Vehicle accidents caused by drowsy (sleepy) driving exceed those caused by alcohol and drugs combined (!)

  • After being awake for nineteen hours (so getting up at 5am to go to work, and returning home after an after-work gathering at around midnight), people who were sleep-deprived were as cognitively impaired as those who were legally drunk.

📍 The shorter your sleep, the shorter your life span.

📍 The physical & mental impairments caused by one night of bad sleep dwarf those caused by an equivalent absence of food or exercise.

📍 Sleep is the single most effective thing we can do to reset our brain and body health each day.

📍 Midnight is supposed to be “mid-night.” Instead, for many of us, it’s usually the time when we consider checking our email one last time.

📍 Sleep-The-Night-Before Learning: Sleep restores the brain’s capacity for learning, making room for new memories.

📍 Sleep is like clicking the “save” button. It protects newly acquired information against forgetting.

📍 Students who stay up late cramming for tests experience a 40% deficit in their ability to make new memories relative to those that get a full nights sleep.

📍 Adults 45+ who sleep <6 hours are 200% more likely to have a heart attack or stroke compared to those sleeping 7-8 hours.

📍 The less you sleep, the more you are likely to eat. Also, insufficient sleep is linked to obesity. That's because short sleep causes the body to deplete muscle mass and retain fat.

📍 Your immune response suffers after a single night of reduced sleep.

📍 A study across four large US companies found that insufficient sleep cost almost $2,000 per employee per year in lost productivity.

📍 Insufficient sleep robs most nations of more than 2 percent of their GDP.

📍 Creativity, intelligence, motivation, effort, efficiency, effectiveness when working in groups, as well as emotional stability, sociability, and honesty. All of these things are systematically dismantled by insufficient sleep.

📍 People are much more likely to lie, cheat, steal, and blame others for their mistakes when they sleep six or less hours.

Environmental adjustments, not sleeping pills, are among the most effective treatments for insomnia.

Here are some great sleep hygiene recommendations proven by science:

  • Avoid artificial light in the evening, especially blue LED lights. Artificial lights suppress melatonin, a hormone triggered by darkness that helps our brain know when to start sleeping. If you’re surrounded by lights at night, then melatonin levels do not rise appropriately. One study found even reading on an iPad versus a print book suppressed melatonin levels by 50% and delayed the onset of sleep by many hours.

  • Decrease your body’s core temperature to initiate sleep more easily. To fall asleep, your inner temperature must fall by 1 degree celsius. This is probably related to nighttime being naturally colder than daytime. So keep your room on the cool side rather than the warm side. A warm bath can also help, because body temperature actually decreases a lot after you get out of the bath due to dilated blood vessels.

  • Go to bed and wake up at the same time each night. This is Matthew Walker’s number one sleep improvement recommendation. Keep this bedtime constant and stick to your sleep schedule even on weekends.

  • Don’t lie awake in bed for more than 20 minutes. If you can’t sleep, go do something relaxing for a while and then return and try to sleep again. Doing something relaxing before bed also helps soothe mental anxiety and decreases heart rate which in turn decreases body temperature. This tip helps many struggling with insomnia.

  • You should also try to get a good amount of natural sunlight during the day. This will help your body regulate your sleep pattern. Another trick is to open your bedroom curtains before you hop into bed, so that the sun, and not an alarm, is what rouses you in the morning.

  • Exercise is great, but not too late in the day. Try to exercise at least thirty minutes on most days but not later than two to three hours before your bedtime.

  • Avoid caffeine, nicotine and alcoholic drinks before bed.

  • Avoid large meals and beverages late at night.

  • If possible, avoid medicines that delay or disrupt your sleep.

  • Don’t take naps after 3 p.m.

  • Relax before bed. Don’t overschedule your day so that no time is left for unwinding. A relaxing activity, such as reading or listening to music, should be part of your bedtime ritual.

5 Key Takeaways

  1. Getting enough quality sleep is even more important to our physical and mental health than diet and exercise.

  2. Compared to other animals, humans experience a disproportionately large amount of REM sleep which fine-tunes our emotional circuits and fuels creativity.

  3. Quality sleep becomes more difficult as we age, but it’s still as important.

  4. Sleep is beneficial to learning. It frees up space for new memories and helps us remember new information.

  5. It’s impossible to “make up” a debt of lost sleep.


This books makes one message absolutely clear: we need to increase sleep awareness and shouldn’t underestimate the power and importance of slee

And if you don’t feel like reading the book why not check out the Ted Talk series “Sleeping with Science with Matthew Walker.


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